The present invention relates to a gas-insulated switchgear or switching apparatus, and more particularly, to a gas-insulated switchgear or switching apparatus which has a three-phase disconnecting switch arranged in a cable head housing.
In a gas-insulated switching or switchgear apparatus, a suitable gas such as Sulphur Hexafluoride (SF.sub.6), having excellent electric insulating properties, is contained within a gas-tight container or housing of metal, with the container or housing being grounded. A high voltage member is disposed within the container or housing in an electrically insulated relationship with respect to the container or housing through insulator means. By virtue of the fact that the electrically insulating gas (SF.sub.6) is used for the electrical insulation of the high voltage member from ground, the distance required for the electrical insulation between the high voltage member and ground can be reduced as compared with air-insulated switching gear apparatuses. Therefore, the construction or insulation space of the switchgear apparatus can be remarkably considerably reduced.
Presently, in order to further reduce the construction or insulation space and to provide for an economical switching apparatus, it has been proposed in, for example, U.S. Pat. No. 4,262,323 to provide a gas insulated electrical apparatus wherein three-phase high voltage members including bus bar conductors are arranged in a common housing, with a cable head being provided for introducing electrical power from or to an external apparatus. A disconnecting switch is provided between the cable head and the circuit breaker, with the disconnecting switch being provided in a housing between the circuit breaker and the cable head.
A disadvantage of the above proposed construction resides in the fact that a considerable amount of space is required between the cable head and the circuit breaker; therefore, it is desirable to arrange the disconnecting switch in a housing of the cable head for reducing the space between the cable head and the circuit breaker.
In a three-phase disconnecting switch, there are many movable members and stationary members, and the high voltage members such as, for example, the bus bar conductors, are supported by insulators so that the high voltage members are insulated from the housing. Consequently, a problem arises as to how the disconnecting switch should be arranged or, more particularly, how the insulators should be arranged for reducing the overall size of the disconnecting switch.
The aim underlying the present invention essentially resides in providing a gas-insulated switchgear or switching apparatus having a smaller or reduced disconnecting switch disposed in a cable head housing of the switchgear apparatus.
More particularly, in accordance with advantageous features of the present invention, a gas-insulator switchgear apparatus is provided which includes a three-phase circuit breaker containing three-phase interrupting parts in a housing, a three-phase disconnecting switch connected to the circuit breaker, a cable head connected to the disconnecting switch, and a cable head housing in which the disconnecting switch and the cable head are accommodated. The disconnecting switch includes three-phase stationary conductors which are respectively electrically connected to the interrupting parts of the circuit breaker, and three-phase connecting conductors are respectively connected to the conductors of the cable head. The three-phase movable conductors are respectively slidably supported by the connecting conductors and are adapted to be respectively contacted to the stationary conductors. Movable insulators are respectively connected to the movable conductors, and stationary insulators respectively support the connecting conductors. The movable insulators and the stationary insulators are arranged so that the two types of insulators, namely, the movable insulators and stationary insulators, respectively form triangles in substantially the same plane, with one of the triangles being inverted relative to the other.
Advantageously, in accordance with further features of the present invention, the stationary insulators are supported by a common plate which is fixed to the cable head housing.
In accordance with still further features of the present invention, the movable insulators are supported by a T-shaped plate which is connected to an operating mechanism.
Advantageously, the stationary conductors are supported by an insulating spacer and grounding or earthing switch is provided in the cable head housing, with stationary contactors of the earthing or grounding switch being respectively mounted on the connecting conductors of the disconnecting switch.
Accordingly, it is an object of the present invention to provide a gas-insulated switchgear apparatus which avoids, by simple means, shortcomings and disadvantages encountered in the prior art.